Methods for forming an organic layer in an organic electroluminescent element include a vacuum deposition method and a wet film-forming method. A vacuum deposition method is advantageous in that lamination is easy, and thus it is easy to improve charge injection from the anode and/or cathode and confine excitons in the light-emitting layer. Meanwhile, a wet film-forming method is advantageous in that no vacuum process is required, it is easy to achieve a large area, and a layer containing several materials with various functions can be easily formed by using a coating liquid prepared by mixing several materials with various functions, for example.
However, according to a wet film-forming method, lamination is difficult. Therefore, as compared with elements obtained using a vacuum deposition method, wet film-forming methods are inferior in terms of driving stability and, except for some instances, have not reached a practical level at present.
Thus, in order to perform lamination by a wet film-forming method, a charge-transporting polymer having a crosslinkable group has been desired and developed. For example, Patent Documents 1 to 4 disclose an organic electroluminescent element containing a specific charge-transporting polymer and laminated by a wet film-forming method.
However, these elements have the problems of high driving voltage, low luminance, and short driving life.